Trifluoromethyltoluenes are useful intermediates for producing agricultural chemicals as is described in DE 3816253, 1 Dec. 1988; JP 63280033, 17 Nov. 1988; and JP 63280034, 17 Nov. 1988.
For example, meta-trifluoromethyltoluene can be converted to the agricultural intermediate m-trifluoromethylphenylacetonitrile by chlorination of m-trifluoromethyltoluene followed by reaction with cyanide.
Consideration has been given to selectively reducing trifluoromethylbenzonitriles and trifluoromethylbenzylamines, many of which are commercially available, to trifluoromethyltoluenes.
Direct reduction of nitriles and amines to methyl groups has been addressed by others. Typically, harsh conditions were required to effect the removal of the nitrogen. These conditions can cause reduction of aromatic rings.
Brown, G. R., Foubister, A. J., Synthesis, 1982, 1036-1037, disclose the reduction of cyano groups to methyl groups using ammonium formate as the hydrogen source in the presence of 10% Pd/C catalyst.
Selection of a reduction catalyst which does not produce reduction of aromatic rings, which provides selective reduction in converting nitrile or aminomethyl to methyl without reducing trifluoromethyl to methyl and which provides high conversion of starting material resulting in high yields, is not taught in the prior art.
Consideration was given to various catalysts including palladium on alumina for the above purpose. Untreated palladium on alumina is too active to use in conversion of trifluoromethylbenzonitriles and trifluoromethylbenzylamines to trifluoromethyltoluenes resulting instead in consuming of starting material by defluorination and ring hydrogenation as well as deamination.